|
||||||
The helminth parasites of the sheathbill, Chionis alba (Gmelin), and the diving petrels, Pelecanoides georgicus (Murphy and Harper) and P. urinatrix (Gmelin), at Bird Island, South Georgia |
||
I. C. WILLIAMS,* N. V. JONES,* M. J. PAYNEf and C. ELLIS* * Department of Zoology, The University, Hull ana f British Antarctic Survey, Monks Wood Experimental Station, Abbots Ripton, Huntingdon, England |
||
ABSTRACT Twelve sheathbills, Chionis alba, 12 South Georgian diving petrels, Pelecanoides georgicus, and 5 common diving petrels, P. urinatrix, collected at Bird Island, South Georgia, were examined for helminth parasites. These appear to be the first helminthological examinations of birds from South Georgia. Eleven of the 12 sheathbills were infected with helminth parasites and the pattern of infection of adult male and female birds was similar. Five species of helminths were found in sheathbills, namely Gymnophallus deliciosus, Notocotylus chionis, Paramonostomum signiensis, Lateriporus australis and Corynosoma hammani. Two species, nameTetrabothrius sp. and Stegophorus heardi, were found in both Pelecanoides georgicus and P. urinatrix. The helminth parasites of whales and seals in the Antarctic and Subantarctic have been extensively studied, while in comparison those of birds from these regions have been neglected. As far as we are aware there are no previous reports on helminth parasites from the sheathbill, Chionis alba (Gmelin), the South Georgian diving petrel, Pelecanoides georgicus (Murphy and Harper), and the common diving petrel, P. urinatrix (Gmelin), from South Georgia. |
||
MATERIAL AND METHODS |
||
Twenty-nine
birds, comprising 5 juvenile and 7 adult C. alba, one chick and 11
adull P. georgicus and 5 adult P. urinatrix,
were
collected by
MJP on Bird Island, South Georgia (54°S, 38°W), in March 1972.
The sheathbills were immediately deep-frozen while the petrels were dissected
and the gut from oesophagus to rectum removed and preserved in 5 % formalin. |
||
RESULTS |
||
The
condition of the birds appeared to be good and no evidence of disease
was noted on examination of the specimens. The
body weights of C. alba immediately after thawing lay within the normal range reported by Jones
(1963) for juvenile and adult sheathbills towards the end of the breeding
season at Signy Island, South Orkney Islands. The weights of the present
specimens were: juveniles, range 485-601 g, mean + S.E. 559 ± 20
g; adults 573-733, 640 + 25 g. No information is available on the weights
of the petrels, (a) Chionis alba. Eleven of 12 sheathbills examined were infected with helminth parasites (Table 1). The following species were found: trematodes, Gymnophallus deliciosui (Olsson, 1893) (gall bladder), Notocotylus chionis Baylis, 1928 (intestinal caeca), Paramonostomum signiensis Jones & Williams, 1969 (rectum); cestodes, Lateriporus australi: Jones & Williams. 1967 ("third fifth of the intestine"!: Acanthocenhala. Corvnnsoma hamman. (von Linstow, 1892) (third fifth of the intestine). No nematodes were found. The pattern of infection of adult male and female sheathbills was similar. |
||
 |
||
All specimens of G. deliciosus were gravid. In the absence of surface spines and possession of a thin tegument they resemble specimens of G. deliciosus obtained from sheathbills at Signy Island, South Orkneys, and differ markedly from the heavily-spined representatives of the species commonly found in gulls in the North Atlantic, North Sea and Barents Sea (Jones and Williams, 1968). The morphological features of N. chionis, P. signiensis, L. australis and C. hammani found in sheathbills in the present study agree closely with accounts of these sepecies given by Jones & Williams (1967, 1968, 1969a, 1969b). Among the 5 juvenile sheathbills were two siblings. These differed remarkably in body weight as well as in helminth infection. One bird, which weighed 486 g, was infected with 6 C. hammani, while the other, weighing 601 g, harboured 2 C. hammani, 18 G. deliciosus. UN. chionis and 2 L. australis. (b) Pelecanoides georgicus and P. urinatrix. One species of tapeworm, namely Tetra-bothrius sp., and one species of nematode, Stegophorus heardi Mawson, 1953, were found in both P. georgicus and P. urinatrix. Unfortunately the single specimens of Tetrabothriui sp., found in the second fifth of the intestine of one of 12 P. georgicus and one of 5 P. urinatrix, were immature and so no specific identification can be given. As far as we are aware there is no previous record of Tetrabothrius from P. georgicus, though Prudhoe (1969) reported T. heteroclitus (Diesing, 1850) and two distinct Tetrabothrius sp. from P. urinatri* collected at lies de Kerguelen in 1929 and 1930 by members of the British, Austalian and New Zealand Antarctic Research Expedition 1929-31. A total of 12 specimens of Stegophorus heardi, comprising 6 adult males, 4 adult females and 2 juvenile females, were found in the oesophagus and stomach of the chick and 2 of 11 P. georgicus and in 3 of 5 adult P. urinatrix. This seems to be the first record of S. heard. from P. urinatrix though the original description of the species, given by Mawson (1953). was based on fragmentary specimens from a stormy petrel, Oceanites oceanicus (Kuhl), and a South Georgian diving petrel, P. georgicus, collected in 1949 at Heard Island (53' 1 ° S 73' 23° E). From examination of the present specimens of S. heardi, and study of the litera¬ture, it is clear that the various species attributed to the genus Stegophorus Wehr, 1934. require a thorough review to establish morphological characters of systematic reliabilitj and to determine the limits of variability of the different alleged species. |
||
DISCUSSION |
||
None of the 7 species of helminth parasites reported here has been
found previously in birds at South Georgia, while Tetrabothrius sp. has
not been recorded before from P. georgicus nor Stegophorus
heardi from
P. urinatrix. The presence of G. deliciosus, N. chionis, L. australis and C. hamtnani in juvenile sheathbills indicates a local source of infection as these birds had not left South Georgia before they were captured. Seasonal movements of sheathbills to and from South Georgia are not well known, but Jones (1963) recorded a general, though incomplete, northward movement from the South Orkney Islands during the winter. It is thus possible that South Georgia sheathbills may overwinter in South America and the Falkland Islands, but they may prove to be resident as they can obtain food from the marine littoral throughout the winter. If this is so then there must also be a local source of infection with Paramonostomum ngniensis. Not unexpectedly the helminth fauna of sheathbills at South Gergia resembles that of sheathbills at Signy Island, South Orkney Islands. There is, however, considerable scope for study of the helminth parasites of Antarctic and Subantarctic birds, especially petrels, as well as the discovery of the intermediate hosts. |
||
|